HVAC is critical for the warehouses because a lot of products are sensitive to temperature or humidity and dust and no consumer likes to get damaged or defective products.
The key functions of a HVAC system in a warehouse are two-fold – maintaining the ambient air temperature or humidity to the desired levels for staff to work effectively and to maintain the Indoor Air Quality (IAQ) of the space to the acceptable standards. ASHRAE 62.1 2010 lays down the acceptable ventilation rates for warehouses. It is typically 10 cfm/per person but will depend on other factors as well such as outside air quality, type of work etc.
The temperature that is typically maintained in warehouses is around 28 Degrees centigrade with a variance of 1 – 2 degrees. While no humidity standards are defined for warehouses specifically, the design aims for a humidity range of 55 – 65 per cent.
The warehouse HVAC requirements can be segregated to two areas – the stowage section and the non-stowage section. The non-stowage section will cover the office, rest rooms, recreational areas etc.
Stowage Area HVAC: Most warehouses are single storey, big box designs where the stowage racks are positioned. The racks may be 2 – 3-meter-high in smaller warehouses or be as high as 20 meter in large, automated warehouses. If there are no grocery or perishable items in the warehouse, then the space is only ventilated and not air conditioned. There are three main approaches that designers take to provide ventilation for warehouses
Ceiling fans: The most basic approach is to install ceiling fans across the warehouse stacking zone. These fans circulate the air at a constant rate and help maintain an even temperature across the workspace. The cost of operation is low. However, the fans are not very effective in maintaining the humidity and do not provide enough comfort in peak summers where ambient temperatures are high in the northern plains where a large no of warehouses are set up. This arrangement is suitable for smaller warehouse set ups with low ceiling heights.
Exhaust fans: When the warehouse stores materials that give of fumes or have Volatile Organic Compounds (VOC), then a more effective way to provide good air quality inside the space is to use exhaust fans. These will pull out the indoor air and outside air will enter from the loading bays or other openings. A factor that needs to be considered is that the quality of outside air may not be good so filtration may be needed. Also, exhaust fans have a higher noise level which may impact the staff’s productivity. Another difficulty with exhaust fans is that the air flows get restricted due to the stowage systems which results in hot and cold spots or in adequate ventilation in many areas. Roof mounted, wind turbines are quite popular in warehouses as they have low operating costs and the noise levels are also low.
HVLS Fans: Where the warehouse floor plate is very large and there is enough height, High Volume, Low Speed (HVLS) fans are used. These fans have large radial diameters and provide a column of air downwards as well as outwards which helps circulate the air more effectively than ceiling mounted fans. These fans are also more energy efficient and hence operating costs are low.
Air Washers: Where the ambient temperatures are on the higher side and the products stowed in the warehouse are temperature sensitive, air washers are used. Outside air is passed over cooling pads and through evaporative cooling, the air temperature reduces.
Non-Stowage Area HVAC: The approach to provide HVAC to non-stowage areas in a warehouse is like that of office or recreational space design. Since the spaces are not very large as compared to the warehouse, the typical solution is use of smaller package units.
Ventilation of warehouses is important not only for maintaining desired air quality for the staff working there but also to prevent damage to the products that are stored. E-commerce supply chain relies heavily on good quality warehouses where products can be shipped, sorted for dispatch and stowed for future use. The staff working in warehouses are mostly blue collar but the whole distribution system relies heavily on this staff for stowage, retrieval and packaging of the products and hence, good ventilation of the space is essential. With the requirement of warehouses set to increase exponentially, the need for more advanced ventilation systems will arise and will further help in making the supply chain more effective.